The operator of the crippled Fukushima Daiichi nuclear power plant, Tokyo Electric Power Co (TEPCO), says some eight tons of radioactive water has leaked from a reactor at the plant.
TEPCO said there was no cause for alarm, since none of the water reached outside the reactor building.
TEPCO said freezing temperatures may have caused a pipe to burst in the building.
The huge earthquake and tsunami that followed caused Japan's biggest civilian nuclear disaster in March.
Compiled from Reuters reports
TEPCO said there was no cause for alarm, since none of the water reached outside the reactor building.
TEPCO said freezing temperatures may have caused a pipe to burst in the building.
The huge earthquake and tsunami that followed caused Japan's biggest civilian nuclear disaster in March.
Compiled from Reuters reports